JPH02151783A - Apparatus for detecting charging state of battery - Google Patents

Abstract

PURPOSE:To securely detect a charging state of a battery by a method wherein a plurality of average values of one of battery discharging current and battery voltage which are regularly fluctuating at the time of starting a starter are obtained while the other indicates a predetermined value. CONSTITUTION:A starter 2 is connected to a battery 1 via a charge generator 71, electric load 72 and a starter switch 21. Voltage of the battery 1 is detected by a voltage detector 4 and input to a computer 5, while discharge current of the battery 1 is detected by a current detector 3 and input to the computer 5. When the switch 21 is turned on, the starter 2 is supplied from the battery 1 and started, and discharge current fluctuating regularly flows while battery voltage also fluctuates. The computer 5 has a storage part 51 and an arithmetic unit 52, and the storage part 51 reads and stores two continuous battery voltages when discharge current indicates a predetermined value. The arithmetic unit 52 calculates the average of the two battery voltages and displays a charging state of the battery on a battery state display 61 according to this average value.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a battery charge state detection device.

[Prior Art] Knowing the state of charge of a battery makes it possible to take measures to prevent the battery from dying, which is extremely convenient.

Therefore, for example, in Japanese Patent Application Laid-open No. 53-127646,
A monitoring device has been proposed that calculates the internal impedance of a battery from the battery discharge current and battery voltage, and determines the state of charge based on the internal impedance, which increases as the state of charge of the battery deteriorates.

[Problems to be Solved by the Invention] The above-mentioned monitoring device is excellent in that it can determine the state of charge of the battery purely electrically. When attempting to easily calculate impedance, there is a problem in that errors occur in the calculated values.

SUMMARY OF THE INVENTION The present invention has been made to solve this problem, and it is an object of the present invention to provide a battery state-of-charge detection device that can calculate the internal impedance without error and reliably know the state of charge of the battery.

[Means for Solving the Problems] As a result of conducting various tests, the inventors came to the conclusion that the cause of the above-mentioned error is that the battery voltage is affected by the previous discharge history.

That is, as shown in FIG. 3 (1), even if the battery discharge current changes in a steep step-like manner, the battery voltage remains unchanged after the delay time Td1. It changes with Td2 (Fig. 3 (2)
). The battery discharge current when starting the starter is shown in Figure 4 (1
), there is a difference in battery voltage between points a and b in the figure, where the discharge current shows the same value. In other words, when the discharge current changes from a small value to a large value (point a in the figure), the battery voltage appears higher (Vl), and in the opposite case, it appears lower (point b in the figure) (■2). . As is clear from the above figure, the battery discharge current at the time of starting the starter has a periodic repetition of almost the same waveform, and therefore the discharge history at the points a and b is almost completely opposite.

Based on this knowledge, the state of charge detection device of the present invention, as shown in FIG.
, means 4 for detecting battery voltage, and storage means 5 for successively storing a plurality of battery voltages when the discharge current, which periodically fluctuates when starting the starter, shows a predetermined value.
1, and calculation means 52 for calculating the average value of the plurality of stored battery voltages.

Alternatively, the battery, the discharge current detection means, the battery voltage detection means, and the memory means for storing a plurality of inherited discharge currents when the battery voltage, which periodically fluctuates when starting the starter, shows a predetermined value; It also includes calculation means for calculating the average value of the plurality of stored discharge currents.

[Operation] In the state of charge detection device having the above configuration, since a plurality of successively stored battery voltages have discharge histories that are almost opposite to each other, by calculating the average value of these battery voltages, , the influence of each other's discharge history is canceled out, and the true battery voltage is obtained. Since this battery voltage is a value obtained when the battery discharge current shows the same value, it indicates the internal impedance of the battery, and thereby the state of charge of the battery can be accurately known.

In addition, by obtaining multiple battery discharge currents when the battery voltage shows the same value and calculating the average value of these, the true value of the discharge current for the battery voltage can be obtained, and from this, accurate internal impedance can also be determined. This allows you to reliably know the state of charge of the battery.

In the first embodiment shown in FIG. 1, a battery 1 includes a charging generator 71 for charging it, an electric load 72, and a starter switch
A starter 2 is connected via 1. The voltage of the battery 1 is detected by the voltage detector 4 and input into the computer 5, and the discharge current of the battery 1 is detected by the current detector 3 and input into the computer 5.

When the starter switch 21 is turned on, the starter 2 is started by being supplied with power from the battery 1, and as shown in FIG. 4, a periodically fluctuating discharge current flows, and the battery voltage also fluctuates accordingly.

The computer 5 has a storage section 51 and a calculation section 52,
The storage unit 51 stores that the discharge current is a predetermined value (for example, 150A).
) (points a and b in the figure), two successive battery voltages 1 and V2 are read and stored. Then, the calculation unit 52 calculates the average value V AVE of the battery voltages (1) and (2) above.
is calculated, and the state of charge of the battery is displayed on the battery state display 61 based on this average value V AVE.

[Second Embodiment] In this embodiment, the present invention is applied to a device that detects the specific gravity of battery fluid during engine operation and improves the battery charging state based on this. The above specific gravity well represents the state of charge of the battery, but it is affected not only by the state of charge but also by moisture evaporation in the battery fluid, so it is necessary to correct the specific gravity when starting the engine.9 Therefore, for an unused battery, The specific gravity of the battery fluid with respect to each battery voltage is determined in advance as the theoretical specific gravity SA in a state of discharging at a predetermined current, and the average voltage value V at the time of starting the starter, obtained with the same configuration as the first embodiment, is obtained under AVE. The specific gravity SB is corrected, and the battery fluid specific gravity during engine operation is corrected using this correction amount to determine the state of charge.

This will be explained in detail below.

In FIG. 2, a specific gravity sensor 8 is attached to the battery 1, and the specific gravity of the battery fluid obtained from this sensor is inputted to the computer 5. The computer 5 includes a voltage measuring section 5
3, a correction value calculation section 54, a specific gravity correction section 55, and a power generation control section 56. The voltage measuring section 53 is
It is composed of the storage section 51 and calculation section 52 of the first embodiment, and inputs the battery voltages (1) and (2) whose discharge currents are at predetermined values, and outputs their average value VAVE.

The correction value calculation unit 54 calculates the battery voltages ■1, ■
The specific gravity below 2 is defined as the actually measured specific gravity S8, and the difference between this and the theoretical specific gravity SA is calculated as the correction value ΔS.

After starting the engine, the detected specific gravity Sr is adjusted to the above correction value Δ
S to obtain the true specific gravity Sr-, and the power generation control unit 56 controls the charging generator 7 so that this specific gravity Sr' is always within a predetermined range.
The regulated voltage of battery 1 is changed to maintain the charging state of battery 1 appropriately.

Note that if the average value V AVE is lower than the voltage required to start the starter, the life indicator 62 is lit to prompt the battery 1 to be replaced.

Thus, by obtaining the true battery voltage in the voltage measuring section 53, specific gravity correction can be performed accurately.

In each of the above embodiments, the battery voltage average value is calculated from a pair of measured voltages, but the accuracy can be further improved if the average value is calculated from a larger number of measured voltages.

Furthermore, instead of calculating the average value of the battery voltage when the battery discharge current shows a predetermined value, it is also possible to calculate the average value of the discharge current when the battery voltage shows a predetermined value. Impedance can be obtained and accurate determination of battery state of charge is possible.

[Effects of the Invention] As described above, the battery state of charge detection device according to the present invention detects the average of a plurality of periodically fluctuating battery discharge currents or battery voltages when the other one shows a predetermined value when starting the starter. By obtaining the value, it is possible to accurately know the battery's internal impedance without error, and thereby the charging state of the battery can be reliably detected.

[Brief explanation of the drawing]

1 and 2 are the first and second embodiments of the present invention, respectively.
A block diagram of the overall configuration of the device in the example. Fig. 3 is a diagram showing the change in battery voltage over time when the battery discharge current changes stepwise. Fig. 4 is a diagram showing the change in battery discharge current and battery voltage over time when starting the starter. It is a figure showing a change. 1...Battery 2...Starter 3...Current detector (discharge current detection means) 4...Voltage detector (battery voltage detection means) 5...Computer 51...Storage unit (storage means) ) 52...Calculating unit (calculating means) Figure 2 Figure 3 Time Figure 4 Time

Claims (2)

[Claims] (1) A battery, a starter supplied with power from the battery, means for detecting a discharge current of the battery, a means for detecting a battery voltage, and a means for detecting a battery voltage such that the discharge current that periodically fluctuates at the time of starting the starter reaches a predetermined value. What is claimed is: 1. A state of charge detection device for a battery, comprising: a storage means for successively storing a plurality of battery voltages at times indicated by the number of battery voltages; and an arithmetic means for calculating an average value of the plurality of stored battery voltages. (2) A battery, a starter supplied with power from the battery, means for detecting discharge current of the battery, means for detecting battery voltage, and the battery voltage, which periodically fluctuates when the starter is started, is set to a predetermined value. What is claimed is: 1. A state of charge detection device for a battery, comprising: storage means for successively storing a plurality of discharge currents at the times shown in FIG.